This invention relates generally to semiconductor structures and methods for fabricating such structures.
As is known in the art, semiconductor devices formed on a single crystal body may be isolated from one another by forming isolation grooves between such devices. The isolation grooves extend from the surface of an epitaxial layer formed on a semiconductor substrate through such epitaxial layer into the substrate. Air, or an oxide having a dielectric constant preferably less than the dielectric constant of the crystal body in the grooves, provides dielectric isolation between the semiconductor devices. It is sometimes desirable to increase the degree of isolation by forming high conductivity regions having impurities of a conductivity type opposite to that of the conductivity type of the epitaxial layer in the substrate beneath the bottom walls of the isolation grooves. While various techniques have been suggested for forming such regions, such techniques are relatively complex, unreliable and otherwise ineffective in producing high yield, high density, low cost monolithic integrated circuits.